[PATCH v5 2/7] pretty: Allow %(trailers) options with explicit value

[Anders Waldenborg <anders@0x63.nu>]

In addition to old %(trailers:only) it is now allowed to write
%(trailers:only=yes)

By itself this only gives (the not quite so useful) possibility to have
users change their mind in the middle of a formatting
string (%(trailers:only=true,only=false)). However, it gives users the
opportunity to override defaults from future options.

Signed-off-by: Anders Waldenborg <anders@0x63.nu>
---
 Documentation/pretty-formats.txt | 14 ++++++---
 pretty.c                         | 52 +++++++++++++++++++++++++++-----
 t/t4205-log-pretty-formats.sh    | 18 +++++++++++
 3 files changed, 73 insertions(+), 11 deletions(-)

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 86d804fe97..d33b072eb2 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -225,10 +225,16 @@ endif::git-rev-list[]
                           linkgit:git-interpret-trailers[1]. The
                           `trailers` string may be followed by a colon
                           and zero or more comma-separated options:
-** 'only': omit non-trailer lines from the trailer block.
-** 'unfold': make it behave as if interpret-trailer's `--unfold`
-   option was given. E.g., `%(trailers:only,unfold)` unfolds and
-   shows all trailer lines.
+** 'only[=val]': select whether non-trailer lines from the trailer
+   block should be included. The `only` keyword may optionally be
+   followed by an equal sign and one of `true`, `on`, `yes` to omit or
+   `false`, `off`, `no` to show the non-trailer lines. If option is
+   given without value it is enabled. If given multiple times the last
+   value is used.
+** 'unfold[=val]': make it behave as if interpret-trailer's `--unfold`
+   option was given. In same way as to for `only` it can be followed
+   by an equal sign and explicit value. E.g.,
+   `%(trailers:only,unfold=true)` unfolds and shows all trailer lines.
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will
diff --git a/pretty.c b/pretty.c
index b83a3ecd23..b8d71a57c9 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1056,13 +1056,25 @@ static size_t parse_padding_placeholder(struct strbuf *sb,
 	return 0;
 }
 
-static int match_placeholder_arg(const char *to_parse, const char *candidate,
-				 const char **end)
+static int match_placeholder_arg_value(const char *to_parse, const char *candidate,
+				       const char **end, const char **valuestart, size_t *valuelen)
 {
 	const char *p;
 
 	if (!(skip_prefix(to_parse, candidate, &p)))
 		return 0;
+	if (valuestart) {
+		if (*p == '=') {
+			*valuestart = p + 1;
+			*valuelen = strcspn(*valuestart, ",)");
+			p = *valuestart + *valuelen;
+		} else {
+			if (*p != ',' && *p != ')')
+				return 0;
+			*valuestart = NULL;
+			*valuelen = 0;
+		}
+	}
 	if (*p == ',') {
 		*end = p + 1;
 		return 1;
@@ -1074,6 +1086,35 @@ static int match_placeholder_arg(const char *to_parse, const char *candidate,
 	return 0;
 }
 
+static int match_placeholder_bool_arg(const char *to_parse, const char *candidate,
+				      const char **end, int *val)
+{
+	char buf[8];
+	const char *strval;
+	size_t len;
+	int v;
+
+	if (!match_placeholder_arg_value(to_parse, candidate, end, &strval, &len))
+		return 0;
+
+	if (!strval) {
+		*val = 1;
+		return 1;
+	}
+
+	strlcpy(buf, strval, sizeof(buf));
+	if (len < sizeof(buf))
+		buf[len] = 0;
+
+	v = git_parse_maybe_bool(buf);
+	if (v == -1)
+		return 0;
+
+	*val = v;
+
+	return 1;
+}
+
 static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 				const char *placeholder,
 				void *context)
@@ -1318,11 +1359,8 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 		if (*arg == ':') {
 			arg++;
 			for (;;) {
-				if (match_placeholder_arg(arg, "only", &arg))
-					opts.only_trailers = 1;
-				else if (match_placeholder_arg(arg, "unfold", &arg))
-					opts.unfold = 1;
-				else
+				if (!match_placeholder_bool_arg(arg, "only", &arg, &opts.only_trailers) &&
+				    !match_placeholder_bool_arg(arg, "unfold", &arg, &opts.unfold))
 					break;
 			}
 		}
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 978a8a66ff..63730a4ec0 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -578,6 +578,24 @@ test_expect_success '%(trailers:only) shows only "key: value" trailers' '
 	test_cmp expect actual
 '
 
+test_expect_success '%(trailers:only=yes) shows only "key: value" trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=yes)" >actual &&
+	grep -v patch.description <trailers >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:only=no) shows all trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=no)" >actual &&
+	cat trailers >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:only=no,only=true) shows only "key: value" trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=yes)" >actual &&
+	grep -v patch.description <trailers >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success '%(trailers:unfold) unfolds trailers' '
 	git log --no-walk --pretty="%(trailers:unfold)" >actual &&
 	{
-- 
2.17.1